Collagenase plays a prominent role in melting of the mammalian cornea consequent to injury or disease. It is our purpose to examine the regulatory factors controlling the production and activity of mammalian corneal collagenase in terms of cellular interactions between epithelium and stromal keratocytes, and also the possible role of lymphocyte factors interacting with collagenase producing cells of the stroma. It is our purpose to explore the relationships between active and inactive collagenase, to isolate and characterize the zymogen or specifically inhibited enzyme, to identify and characterize the activator for this postulate proenzyme, to identify and characterize stimulatory factors from other cell types which influence the activation process. In addition, we hope to examine the effect of hormones, chemical stimulatory substances and experimental Vitamin A deficiency on the above described regulatory mechanism for corneal collagenase production. Since Vitamin A deficiency is a prime cause of blindness due to "melting" of the cornea in many areas of the world there is good reason to explore this syndrome.